Shadow mask rim having integral blisters for locking on locating pins in envelope wall



July 21, 1970 N. B. MEARS 3,521,104

SHADOW MASK RIM HAVING INTEGRAL BLISTERS FOR LOCKING ON LQCATING PINS IN ENVELOPE WALL Filed Feb. 10, 1967 INVENTOR NORMAN B. MEARS A TORNEIYS United States Patent O 3,521,104 SHADOW MASK RIM HAVING INTEGRAL BLISTERS FOR LOCKING ON LOCATING PINS IN ENVELOPE WALL Norman B. Mears, St. Paul, Minn., assignor t Buckbee- Mears Company, St. Paul, Minn., a corporation of Minnesota Filed Feb. 10, 1967, Ser. No. 615,173 Int. Cl. H01j 29/46, 29/82, 1/96 US. Cl. 313-85 2 Claims ABSTRACT OF THE DISCLOSURE An aperture or shadow mask for a colored TV picture tube is provided with a rim with integrally formed detents for latching onto supporting pins embedded in the glass face plate of the tube. The rim is made flexible yet resil ient so that the mask can be unlatched and removed but will return to the same position when it is latched back on.

BACKGROUND OF THE INVENTION Field of the invention Description of the prior art A variety of means for detachably mounting the shadow mask to the face plate have been proposed and used over the years. For example, the pending application Ser. No. 578,858, filed Sept. 12, 1966, by Norman B. Mears, titled Improved Shadow Mask Construction for Colored TV Picture Tubes, and assigned to the same assignee as the instant application, describes one manner of attachment by locating holes in a flange formed around the shadow mask for mating with supporting pins or studs jutting out of the edge of the glass face plate. Another manner of attachment is described, at least in part, in Pat. No. 3,284,884, which describes the use of spring detents mounted on the outside of a rigid frame support for the shadow mask for engaging the locating pins embedded in the glass face plate. The latter illustrates the bulkiness and weight added by the rigid frame support for the mask in addition to illustrating a cumbersome and quite complex jig which is necessary for relocating the mask within the face plate each time the phosphor dots are formed. By comparison, the structural features of the instant invention are such that stability of the shadow mask is achieved with a minimum amount of additional weight and the mask can be attached and removed in a much less complicated manner and yet the miniature openings in the mask will consistently return to the same setting.

SUMMARY The essence of the invention resides in constructing the shadow mask with a flexible but resilient supporting rim which is aflixed along the outer edge of the shadow mask. Detent means are formed integrally with the rim so that any flexing of the rim for latching the detent means will still result in the mask always being relocated at its same setting.

DESCRIPTION OF PREFERRED EMBODIMENT A preferred embodiment of the invention will now be described with reference to the accompanying drawings in which:

FIG. 1 is a rear view showing a shadow mask mounted to the face plate of the picture tube in accordance with the teachings of this invention;

FIG. 2 is a sectional view taken along line 22 of FIG. 1.

Ordinarily the glass bulb of the picture tube is a twopiece construction consisting of a face plate 10 and a conical or tapered rear portion (not shown) which is welded or otherwise jointed to the edge of the surrounding side wall members of the face plate. Jutting inward from the side walls of the face plate 10 are locating pins 16 which have one end embedded or welded or otherwise fixedly attached to the face plate. The pins are constructed with a cylindrical portion which terminates with a frustoconical portion. The inner face of the face plate 10 contains the phosphor colored dots which provide the colors for the viewer. Although various techniques and processes have been developed for forming these phosphor dots on the face plate, in general the present-day methods involve the use of photographic techniques involving steps which are well known to those of ordinary skill in the art. Briefly, this process comprises the steps of initially coating the inside face of the face plate with a sensitized color phosphor, then projecting light onto the phosphor coating through the shadow mask 11, then washing away the unhardened phosphor and then repeating these steps for the second and third primary colors. It can be seen immediately that the locating of the shadow mask when forming the various colored dots on the face plate is quite critical. The myriad of tiny :apertures must return to precisely the same setting each time the shadow mask is detached from the face plate and then secured. For the three color system in present-day color TV, the shadow mask is detached at least three times and resecured at least four times during the dot-forming process.

The shadow mask is ordinarily made out of a sheet of 16 gauge cold rolled steel. The translucent area 12 of the shadow mask 11 is formed by hundreds of thousands of tiny openings having diameters in the order of .01 inch, which pierce the metal. It is through these openings that the electron beams travel from the gun source located at the rear of the picture tube to strike the phosphor layers on the inner face of the face plate. As seen in FIG. 2, the translucent area of the shadow mask is bowed to the contour of the face plate. Around the translucent area an opaque and stiff but resilient metal rim 13 is formed. The rim may be drawn shallow or deep correspondingly forming a bowl-like construction which can be considered shallow or deep and parallels the side walls of the face plate 10 but is spaced away therefrom. In the case of a shallow drawn mask, the outer edge of the mask is preferably welded to the edge of a strip of metal which is formed into a closed loop. This provides a stiffening rim which in effect is the same construction as a deep drawn mask. The rim is particularly characterized by being stiff enough to support the translucent area of the mask so that it will not bend or bow and yet being flexible and resilient enough so that it can be twisted or contorted somewhat and yet return back to its original condition. This characteristic of the metal rim can be achieved in a variety of ways, such as by the selection of suitable material, selection of suitable dimensions, variout processes or treatments such as annealing, etc.

SPECIFICATION FOR PATENT APPLICATION On the rim 13 are blisters or bubbles 14 which may be formed by pressing or by any other convenient fashion.

The present embodiment contains three blisters, one located on the bottom side and one on each of the left and right sides of the rim. Although no limitation is intended, it has been found satisfactory to use three blisters for locating and mounting the mask. Holes 15 are punched or drilled or otherwise formed at the general center of the blister 14 and are dimensioned to accommodate the locating pins 16 which jut inward from the side walls and the bottom wall of the face plate 10. The blisters 14 are formed to dimensions which are selected so that the respectively corresponding locating pins 16 extend far enough into the holes 15 so that the frustoconical portion of the pins set firmly in the holes and press with some force inwardly on the blister 14. With the pins snugly seated within the holes of the blisters in this manner, the rim and the aperture mask are securely mounted to the face plate. The forces exerted by the pins 16 on the blisters 14 may cause some deformation of the latter but this will not be transferred to change the critical location of the translucent area of the mask. It has been found that by flexing the rim 13 the blisters 14 can be unlatched from their corresponding locating pins 16 to enable removal of the mask. To recouple the mask to the face plate, the rim again is flexed enough to position the blisters opposite the corresponding pins so that the pins will snap into position and seat firmly Within the holes 15 of the respectively corresponding blisters 14. This will cause the miniature apertures of the translucent area 12 to return to the same setting as previously.

Although not shown in the drawings, variations of the construction are contemplated. For example, a flange or flare can be formed to extend around and over the rear edge of the rim. This flange may be clipped or otherwise attached to the edge of the rim and can serve as a shield. It is further contemplated that a further shield, which may be shaped to conform to the contour of the rear portion of the picture tube glass envelope, can also be attached to the rim-flange combination to provide even further shielding in a relatively simple construction. These and other variations are possible because of the simplicity of the means for mounting the mask to the face plate and the ease with which it can be uncoupled and remounted without affecting the positioned setting of the apertures.

I claim:

1. For locating and mounting a shadow mask within the glass face plate of a colored TV picture tube where said face plate has locating pins embedded in and extending inward from its side walls, the improvement comprising:

a metallic rim encircling the shadow mask fixedly attached to the mask along the outer edge thereof; said rim extending rearward from the mask and paralleling the glass side walls of the picture tube face plate, detent means comprising a plurality of substantially spherical blisters integrally formed in said rim and jutting outwardly therefrom, said blisters being respectively located opposite said locating pins in the face plate side walls; each of said blisters having a center opening for receiving a corresponding locating pin for locking said mask in position, said rim being sufliciently flexible to unlock from said locating pins by twisting and sufficiently resilient to relock to its same setting.

2. The invention as in claim 1 wherein the locating pins are tapered to seat snugly in the openings in said blisters.

References Cited UNITED STATES PATENTS 6/1960 May. 10/1961 Godfrey.

ROBERT SEGAL, Primary Examiner 

